1. Field of the Invention
The present invention is related to magnetic recording systems, and in particular, to write fringing reduction in discrete track recording.
2. Background Information
Recently, the trend in magnetic recording is to employ perpendicular magnetic recording (PMR) techniques. In perpendicular magnetic recording, the magnetic domains is are aligned perpendicularly to the surface of the disk platter. This allows bits to be placed closer together on the platter, thus increasing storage density to an amount greater than that which has been achieved in conventional longitudinal recording.
A further way to increase bit density is to employ discrete track recording (DTR). In discrete track recording, magnetic information is stored on single tracks in the media zo as opposed to storing the information in a bit patterned media. In a DTR system, adjacent tracks are physically separated by air gaps in the form of grooves. These air gaps are minimized to increase the bit density such that tracks are placed closer together for a high track per inch (TPI) configuration allowing a high bits per square inch count in the media. However, this results in a low magnetic write width (MWW), which can in turn result in write field loss, and thus loss of an overwrite (OVW) from the head. Preferably, the magnetic write width of the head should be as close to the width of the track as possible, however, there still exists a tendency to have some of the field extend outwardly from the head and reach into the adjacent track. Such a field is known as a fringe field. The fringing magnetic flux can travel into the adjacent track leading to adjacent track erasure.
Furthermore, in a standard head media design, the head field in the off-track direction is found to decay slowly. This slow decay is disadvantageous because it adds to further adjacent track erasure as the fringe field decays. It has been challenging to address this problem because the size of the write head, the amount of the fringe field, the fly height of the head, and the interlayer thicknesses in the media are parameters that are involved in the phenomenon, however, such parameters are essentially set and cannot be readily changed. For example, it is unlikely that the head (and therefore the MWW) could be narrowed readily, without the loss of OVW.
To address the writing fringing issue, prior techniques have provided floating side shields in the write head. For example, U.S. Pat. No. RE 33,949 of Mallary, et al., which issued on Jun. 2, 1992, for VERTICAL MAGNETIC RECORDING ARRANGEMENT, provides a write head for perpendicular recording that includes a shield on the write pole tip that decreases the fringing field thus improving signal to noise ration in the recording process. However, the side shield on the pole tip can reduce the field strength of the write field, which is undesirable. Moreover, it is also not desirable to require an additional component to be added to the write pole.
Therefore, there remains a need for a technique for reducing write fringe fields that does not require placing a side shield on the write head, which side shield may result in reduced field strength, and necessitates modifications to head components. There remains a further need for such a technique that is suitable for use in a DTR environment.